The present invention relates to a cooling tower.
FIG. 1 exemplarily shows a conventional cooling tower, which comprises an outlet 3 with an axial flow fan 2 at a top of a casing 1, air inlets 4 at an outer periphery of the casing 1, a hot water vessel 5 at an upper portion of the casing 1 and surrounding the outlet 3, and a heat exchanger 9 below the hot water vessel 5 in which hot water 7 is sprayed through spray ports 6 on a lower surface of the vessel 5 and is heat-exchanged with ambient air 8 sucked through the air inlets 4 by the fan 2. The heat exchanger 9 comprises a dry type air heater 11 in the form of finned tubes 10 immediately below the vessel 5 and fillers 12 in the form of a number of heat transfer surface members with irregular surfaces, made of sheet-like synthetic resin and arranged in parallel with each other to define flow passages for the ambient air 8.
In FIG. 1, reference numeral 13 denotes a bottom water vessel to recover the cooled water.
With the cooling tower of the type described above, the hot water 7 in the vessel 5 flows down through the ports 6 and tubes 10 and passes along the fillers 12 underneath while the ambient air 8 is sucked through the inlets 4 by the fan 2 and is directed to flow transversely of the heater 11 and fillers 12, thereby cooling the water 7.
In this case, the hot water 7 flowing down along the fillers 12 is effectively cooled through direct heat exchange with the ambient air 8. The air 8 having been heat-exchanged with the water 7 at the fillers 12 becomes wet air 14 which is high in temperature and has a moisture content of substantially 100%. If the wet air 14 were directly discharged out of the cooling tower, it would become white smoke when the ambient temperature is low.
Such white smoke will be abhorred by the neighborhood since it seems as if the white smoke would contaminate their environment. Moreover, there is a fear that visibility may be adversely affected by the white smoke coming down near a ground surface and staying there as fog. Thus, there has been strong demands to prevent the generation of white smoke.
To this end, in the cooling tower as shown in FIG. 1 with the hot water 7 flowing down through the tubes 10, the ambient air 8 flowing along outer peripheries of the tubes 10 is heated in dry manner into dry air 15 having an extremely low moisture content. The dry air 15 is mixed with the wet air 14 by the fan 2 to reduce the moisture content of the air to be discharged through the outlet 3, thereby preventing the white smoke being generated.
Such a cooling tower, which is provided with the special-purpose dry type air heater 11 in the form of the finned tubes 10 exclusively for generating the dry air 15 to prevent the white smoke from being generated, is much complicated in structure and extremely expensive in production cost. Because of indirect heat exchange with the finned tubes 10, the heat exchange efficiency cannot be satisfactorily enhanced and in compensation therefore a high volume or capacity is required. This means that the dry type air heater 11 must be larger in size, which leads to increase in height and thus in total dimensions of the cooling tower.
The present invention was made in view of the above and has for its object to reduce cost for construction of and make compact in size a cooling tower which is capable of preventing white smoke from being generated.